The world of polymers has progressed rapidly to transform material science from wood and metals of the 19th Century to the use of thermoset polymers of the mid-20th Century to the use of thermoplastic polymers of later 20th Century.
Thermoplastic compounds are often used in the healthcare industry as hygienically disposable items. Catheters for in-vivo diagnosis and treatment are often constructed from thermoplastic polyurethanes. Optically translucent thermoplastic polyurethanes are preferred because the health care practitioner can see through the wall of the catheter before and during in-vivo usage. Delivery of fluids containing air bubbles could be avoided (producing air emboli if in the blood), for example, by using an optically translucent, medical grade thermoplastic polyurethane.
During in-vivo usage, many diagnostic or therapeutic medical devices are monitored by the use of x-rays, using an energy of 30-70 keV, and other diagnostic electromagnetic radiation. Radiopaque materials in the medical device offer a contrast during such monitoring, such to recognize the precise location of a catheter tip and shaft as it moves within the body of the patient undergoing a medical procedure. Yet radiopaque materials, as helpful during in-vivo usage as they are, have the detriment of reducing severely the optical translucency of medical device before and during an in-vivo usage.
PCT Patent Publication WO95/14501 teaches that a radiopaque material can be present in thermoplastic material in an amount from 5 to 50 percent by weight in levels to be adjusted to achieve both a radiopaque and translucent material for a balloon catheter. But there is no additional detail to explain how to disperse the proper amounts of polymer and radiopaque material. Moreover, this publication does not teach the use of thermoplastic polyurethane as a candidate for the balloon catheter.